Fix returning from game pad options not updating tower color

I was looking through all calls to game.returnmenu(), and I noticed that
the return option in the game pad screen didn't have a
map.nexttowercolour(). I tested it and, yep, returning from there
doesn't update the background color.

So that should be fixed now.

desktop_version/src/Input.cpp

@@ -1233,6 +1233,7 @@ static void menuactionpress(void)
         case 5:
             music.playef(11);
             game.returnmenu();
+            map.nexttowercolour();
             break;
         }
         break;